Reliablity and Validity

The quality of any statistical analysis can be only as good as is the quality of the data upon which it is based; thus, the reliability and validity of data collected for use in statistical analysis is of paramount importance. Validity refers to the extent to which data a data collection instrument, or an analytical procedure (such as a test) measures what it is actually desired to measure. Reliability refers to the accuracy and precision of a data collection procedure or the outcome of an analytical procedure (such as a test). Validity, thus, is the extent to which differences found through a particular data collection procedure or analytical procedure reflects true differences among those variables being measured, while reliability refers to the capacity of an instrument or an analytical procedure to yield similar measurements under similar conditions.

To accomplish the objective of validity in measurement, it is necessary to have some standard that is external to the measurement procedure, in order to evaluate the validity of the procedure. Thus, if it were desired to measure the height of a number of individuals in terms of feet and inches, it would be necessary to have a measuring instrument that was calibrated in feet and inches. The validity of this measuring instrument calibrated in feet and inches would be determined based on its ability to accurately measure feet and inches in accordance

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e instrument does not measure the height of the same individual as being the same in measurement-after-measurement, it is not a reliable measurement instrument. Further, if the instrument does not measure the height of the same individual as being the same in measurement-after-measurement, the instrument, obviously, does not always yield results which are in agreement with the external standard, such as a master instrument maintained by the National Bureau of Standards. Therefore, in this example, because the measuring instrument is not reliable, it cannot be valid. On the other hand, if an instrument does measure the height of the same individual as being the same in measurement-after-measurement, the instrument is a reliable instrument. If, however, this identical time-after-time measurement is not in agreement with that yielded by a previously validated external standard, the reliable instrument is not a valid instrument. Therefore, it can easily be seen that reliability in an instrument is required before that instrument can be considered to be valid, but that reliability in an instrument cannot, alone, guarantee that such instrument will be valid. A validity coefficient is the correlation coefficient between a measuri
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Approximate Word count = 1510
Approximate Pages = 6 (250 words per page)

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